Variable magnification optical system, optical apparatus, and method for producing variable magnification optical system

ABSTRACT

A variable magnification optical system comprising, in order from an object side, a first lens group having negative refractive power, a first intermediate lens group having positive refractive power, a second intermediate lens group having negative refractive power and a rear lens group; upon varying a magnification from a wide angle end state to a telephoto end state, a distance between the first lens group and the first intermediate lens group being varied, a distance between the first intermediate lens group and the second intermediate lens group being varied, and a distance between the second intermediate lens group and the rear lens group being varied; the rear lens group comprising at least one focusing lens group which is moved upon carrying out focusing from an infinitely distant object to a closely distant object; and predetermined conditional expressions being satisfied, thereby the focusing lens group(s) being reduced in weight.

TECHNICAL FIELD

The present invention relates to a variable magnification opticalsystem, an optical apparatus and a method for manufacturing the variablemagnification optical system.

BACKGROUND ART

There has been proposed a variable magnification optical system that issuitable to be used for a photographic camera, an electronic stillcamera, a video camera or the like. For example, refer to JapanesePatent application Laid-Open Gazette No. 2013-160944. However, in theconventional variable magnification optical system a focusing lens grouphas not been made sufficiently light in weight.

PRIOR ART REFERENCE Patent Document

Patent Document 1: Japanese Patent application Laid-Open Gazette No.2013-160944.

SUMMARY OF THE INVENTION

According to the present invention, there is provided a variablemagnification optical system comprising, in order from an object side, afirst lens group having negative refractive power, a first intermediatelens group having positive refractive power, a second intermediate lensgroup having negative refractive power and a rear lens group;

upon varying a magnification from a wide angle end state to a telephotoend state, a distance between said first lens group and said firstintermediate lens group being varied, a distance between said firstintermediate lens group and said second intermediate lens group beingvaried, and a distance between said second intermediate lens group andsaid rear lens group being varied;

said rear lens group comprising at least one focusing lens group whichis moved upon carrying out focusing from an infinitely distant object toa closely distant object; and

the following conditional expressions being satisfied:

0.40<(−f1)/f1Rw<2.00

0.10<BFw/fw<1.00

where f1 denotes a focal length of said first lens group, f1Rw denotes acomposite focal length of all lens groups behind said first lens groupin the wide angle end state, BFw denotes a back focus of said variablemagnification optical system in the wide angle end state, and fw denotesa focal length of said variable magnification optical system in the wideangle end state.

Further, according to the present invention, there is provided a methodfor manufacturing a variable magnification optical system comprising, inorder from an object side, a first lens group having negative refractivepower, a first intermediate lens group having positive refractive power,a second intermediate lens group having negative refractive power and arear lens group; comprising steps of:

constructing such that, upon varying a magnification from a wide angleend state to a telephoto end state, a distance between said first lensgroup and said first intermediate lens group is varied, a distancebetween said first intermediate lens group and said second intermediatelens group is varied, and a distance between said second intermediatelens group and said rear lens group is varied;

constructing such that said rear lens group comprises at least onefocusing lens group which is moved upon carrying out focusing from aninfinitely distant object to a closely distant object; and

constructing such that the following conditional expressions aresatisfied:

0.40<(−f1)/f1Rw<2.00

0.10<BFw/fw<1.00

where f1 denotes a focal length of said first lens group, f1Rw denotes acomposite focal length of all lens groups behind said first lens groupin the wide angle end state, BFw denotes a back focus of said variablemagnification optical system in the wide angle end state, and fw denotesa focal length of said variable magnification optical system in the wideangle end state.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a variable magnification optical systemaccording to a First Example.

FIG. 2A, FIG. 2B and FIG. 2C are graphs showing various aberrations uponfocusing on an infinite distance object, respectively, in the wide angleend state, in the intermediate focal length state, and in the telephotoend state, of the variable magnification optical system according to theFirst Example.

FIG. 3A, FIG. 3B and FIG. 3C are graphs showing various aberrations uponfocusing on a close distance object, respectively, in the wide angle endstate, in the intermediate focal length state, and in the telephoto endstate, of the variable magnification optical system according to theFirst Example.

FIG. 4 is a sectional view of a variable magnification optical systemaccording to a Second Example.

FIG. 5A, FIG. 5B and FIG. 5C are graphs showing various aberrations uponfocusing on an infinite distance object, respectively, in the wide angleend state, in the intermediate focal length state, and in the telephotoend state, of the variable magnification optical system according to theSecond Example.

FIG. 6A, FIG. 6B and FIG. 6C are graphs showing various aberrations uponfocusing on a close distance object, respectively, in the wide angle endstate, in the intermediate focal length state, and in the telephoto endstate, of the variable magnification optical system according to theSecond Example.

FIG. 7 is a sectional view of a variable magnification optical systemaccording to a Third Example.

FIG. 8A, FIG. 8B and FIG. 8C are graphs showing various aberrations uponfocusing on an infinite distance object, respectively, in the wide angleend state, in the intermediate focal length state, and in the telephotoend state, of the variable magnification optical system according to theThird Example.

FIG. 9A, FIG. 9B and FIG. 9C are graphs showing various aberrations uponfocusing on a close distance object, respectively, in the wide angle endstate, in the intermediate focal length state, and in the telephoto endstate, of the variable magnification optical system according to theThird Example.

FIG. 10 is a sectional view of a variable magnification optical systemaccording to a Fourth Example.

FIG. 11A, FIG. 11B and FIG. 11C are graphs showing various aberrationsupon focusing on an infinite distance object, respectively, in the wideangle end state, in the intermediate focal length state, and in thetelephoto end state, of the variable magnification optical systemaccording to the Fourth Example.

FIGS. 12A, 12B and 12C are graphs showing various aberrations uponfocusing on a close distance object, respectively, in the wide angle endstate, in the intermediate focal length state, and in the telephoto endstate, of the variable magnification optical system according to theFourth Example.

FIG. 13 is a sectional view of a variable magnification optical systemaccording to a Fifth Example.

FIG. 14A, FIG. 14B and FIG. 14C are graphs showing various aberrationsupon focusing on an infinite distance object, respectively, in the wideangle end state, in the intermediate focal length state, and in thetelephoto end state, of the variable magnification optical systemaccording to the Fifth Example.

FIG. 15A, FIG. 15B and FIG. 15C are graphs showing various aberrationsupon focusing on a close distance object, respectively, in the wideangle end state, in the intermediate focal length state, and in thetelephoto end state, of the variable magnification optical systemaccording to the Fifth Example.

FIG. 16 is a sectional view of a variable magnification optical systemaccording to a Sixth Example.

FIG. 17A, FIG. 17B and FIG. 17C are graphs showing various aberrationsupon focusing on an infinite distance object, respectively, in the wideangle end state, in the intermediate focal length state, and in thetelephoto end state, of the variable magnification optical systemaccording to the Sixth Example.

FIG. 18A, FIG. 18B and FIG. 18C are graphs showing various aberrationsupon focusing on a close distance object, respectively, in the wideangle end state, in the intermediate focal length state, and in thetelephoto end state, of the variable magnification optical systemaccording to the Sixth Example.

FIG. 19 is a sectional view of a variable magnification optical systemaccording to a Seventh Example.

FIG. 20A, FIG. 20B and FIG. 20C are graphs showing various aberrationsupon focusing on an infinite distance object, respectively, in the wideangle end state, in the intermediate focal length state, and in thetelephoto end state, of the variable magnification optical systemaccording to the Seventh Example.

FIG. 21A, FIG. 21B and FIG. 21C are graphs showing various aberrationsupon focusing on a close distance object, respectively, in the wideangle end state, in the intermediate focal length state, and in thetelephoto end state, of the variable magnification optical systemaccording to the Seventh Example.

FIG. 22 is a sectional view of a variable magnification optical systemaccording to an Eighth Example.

FIG. 23A, FIG. 23B and FIG. 23C are graphs showing various aberrationsupon focusing on an infinite distance object, respectively, in the wideangle end state, in the intermediate focal length state, and in thetelephoto end state, of the variable magnification optical systemaccording to the Eighth Example.

FIG. 24A, FIG. 24B and FIG. 24C are graphs showing various aberrationsupon focusing on a close distance object, respectively, in the wideangle end state, in the intermediate focal length state, and in thetelephoto end state, of the variable magnification optical systemaccording to the Eighth Example.

FIG. 25 is a view showing a configuration of a camera equipped with thevariable magnification optical system.

FIG. 26 is a flowchart schematically showing a method for manufacturingthe variable magnification optical system.

EMBODIMENT FOR CARRYING OUT THE INVENTION

Next, a variable magnification optical system according to the presentembodiment, an optical apparatus and a method for producing the variablemagnification optical system, will be explained.

The variable magnification optical system according to the presentembodiment comprises, in order from an object side, a first lens grouphaving negative refractive power, a first intermediate lens group havingpositive refractive power, a second intermediate lens group havingnegative refractive power and a rear lens group;

upon varying a magnification from a wide angle end state to a telephotoend state, a distance between said first lens group and said firstintermediate lens group being varied, a distance between said firstintermediate lens group and said second intermediate lens group beingvaried, and a distance between said second intermediate lens group andsaid rear lens group being varied;

said rear lens group comprising at least one focusing lens group whichis moved upon carrying out focusing from an infinite distance object toa close distance object; and

the following conditional expressions (1) and (2) being satisfied:

0.40<(−f1)/f1Rw<2.00  (1)

0.10<BFw/fw<1.00  (2)

where f1 denotes a focal length of said first lens group, f1Rw denotes acomposite focal length of all lenses behind said first lens group in thewide angle end state, BFw denotes a back focus of said variablemagnification optical system in the wide angle end state, and fw denotesa focal length of said variable magnification optical system in the wideangle end state.

Here, in the present embodiment, the first intermediate lens group, thesecond intermediate lens group and the rear lens group, each comprise atleast one lens group. Meanwhile, in the present embodiment, a lens groupmeans a portion which comprises at least one lens separated by an airspace.

The variable magnification optical system according to the presentembodiment comprises at least four lens groups and changes distancesbetween the neighboring lens groups upon varying magnification from thewide angle end state to the telephoto end state, thereby being able toattain superb aberration correction upon varying magnification.Moreover, the focusing lens group(s) can be downsized and made light inweight by arranging the focusing lens group(s) in the rear lens group.

The conditional expression (1) defines a ratio of a focal length of thefirst lens group relative to a composite focal length of all lensesbehind the first lens group in the wide angle end state. With satisfyingthe conditional expression (1), the variable magnification opticalsystem according to the present embodiment can correct effectively comaaberration and other various aberrations in the wide angle end state,and can suppress variations in spherical aberration and other variousaberrations upon varying magnification from the wide angle end state tothe telephoto end state.

When the value of (−f1)/f1Rw is equal to or exceeds the upper limit ofthe conditional expression (1) of the variable magnification opticalsystem of the present embodiment, composite refractive power of the lensgroups behind the first lens group in the wide angle end state becomesstrong, and it becomes difficult to correct effectively coma aberrationand other various aberrations in the wide angle end state. Meanwhile, itis preferable to set the upper limit value of the conditional expression(1) to 1.90, further preferable to 1.80 and further more preferable to1.70.

On the other hand, when the value of (−f1)/f1Rw is equal to or fallsbelow the lower limit of the conditional expression (1) of the variablemagnification optical system of the present embodiment, refractive powerof the first lens group becomes strong, and it becomes difficult tosuppress variations in spherical aberration and other variousaberrations upon varying magnification from the wide angle end state tothe telephoto end state. Meanwhile, it is preferable to set the lowerlimit value of the conditional expression (1) to 0.50, furtherpreferable to 0.60 and further more preferable to 0.70.

The conditional expression (2) defines a ratio of a back focus of saidvariable magnification optical system in the wide angle end staterelative to a focal length of said variable magnification optical systemin the wide angle end state. With satisfying the conditional expression(2), the variable magnification optical system according to the presentembodiment can correct effectively coma aberration and other variousaberrations in the wide angle end state. Meanwhile, the term “backfocus” means a distance along the optical axis from the most image sidelens surface to the image plane.

When the value of BFw/fw is equal to or exceeds the upper limit of theconditional expression (2) of the variable magnification optical systemof the present embodiment, the back focus in the wide angle end staterelative to the focal length in the wide angle end state becomes large,and it becomes difficult to correct coma aberration and other variousaberrations in the wide angle end state. Meanwhile, it is preferable toset the upper limit value of the conditional expression (2) to 0.95,further preferable to 0.90 and further more preferable to 0.85, andstill further preferable to 0.80.

On the other hand, when the value of BFw/fw is equal to or falls belowthe lower limit value of the conditional expression (2) of the variablemagnification optical system of the present embodiment, the back focusin the wide angle end state relative to the focal length in the wideangle end state becomes small, and it becomes difficult to correct comaaberration and other various aberrations in the wide angle end state. Itbecomes difficult also to arrange mechanical members of lens barrel.Meanwhile, it is preferable to set the lower limit value of theconditional expression (2) to 0.20, further preferable to 0.25, furthermore preferable to 0.30 and still further preferable to 0.40.

With the above mentioned configurations, it is possible to realize thevariable magnification optical system which has excellent opticalperformance, and in which the focusing lens group(s) is(are) made lightin weight.

In the variable magnification optical system according to the presentembodiment, it is desirable that the following conditional expression(3) is satisfied:

0.70<|fF|/ft<3.30  (3)

where fF denotes a focal length of a focusing lens group having astrongest refractive power in the focusing lens groups, and ft denotes afocal length of the variable magnification optical system in thetelephoto end state.

The conditional expression (3) defines a ratio of a focal length of thefocusing lens group having the strongest refractive power in thefocusing lens groups, relative to a focal length of the variablemagnification optical system in the telephoto end state.

With satisfying the conditional expression (3), the variablemagnification optical system according to the present embodiment cansuppress variations in spherical aberration and other variousaberrations upon carrying out focusing from an infinite distance objectto a close distance object, without making the lens barrel large.

When the value of |fF|/ft is equal to or exceeds the upper limit valueof the conditional expression (3) of the variable magnification opticalsystem according to the present embodiment, refractive power of thefocusing lens group becomes weak, and an amount of movement of thefocusing lens group upon carrying out focusing from the infinitedistance object to the close distance object becomes large so that thelens barrel becomes large in size. Meanwhile, it is preferable to setthe upper limit value of the conditional expression (3) to 3.20 andfurther preferable to 3.10.

On the other hand, when the value of |fF|/ft in the conditionalexpression (3) of the variable magnification optical system according tothe present embodiment, is equal to or falls below the lower limitvalue, refractive power of the focusing lens group becomes strong, andit becomes difficult to suppress variation in spherical aberration uponcarrying out focusing from the infinite distance object to the closedistance object. Meanwhile, it is preferable to set the lower limitvalue of the conditional expression (3) to 0.75, and further preferableto 0.80.

Further, in the variable magnification optical system according to thepresent embodiment, it is desirable that the following conditionalexpression (4) is satisfied:

0.60<f1N/f1<2.20  (4)

where f1N denotes a focal length of a lens having a strongest negativerefractive power in the first lens group, and f1 denotes a focal lengthof the first lens group.

The conditional expression (4) defines a ratio of the focal length ofthe lens having the strongest negative refractive power in the firstlens group to the focal length of the first lens group.

With satisfying the conditional expression (4), the variablemagnification optical system according to the present embodiment cancorrect effectively coma aberration and other various aberrations andsuppress variations in spherical aberration and other variousaberrations upon varying magnification from a wide angle end state to atelephoto end state.

When the value of f1N/f1 is equal to or exceeds the upper limit value ofthe conditional expression (4) of the variable magnification opticalsystem according to the present embodiment, refractive power of thefirst lens group becomes strong, and it becomes difficult to suppressvariations in spherical aberration and other various aberrations uponvarying magnification from the wide angle end state to the telephoto endstate. Meanwhile, it is preferable to set the upper limit value of theconditional expression (4) to 1.90 and further preferable to 1.80.

On the other hand, when the value of f1N/f1 in the conditionalexpression (4) of the variable magnification optical system according tothe present embodiment, is equal to or falls below the lower limitvalue, refractive power of the lens having the strongest negativerefractive power in the first lens group becomes strong, and it becomesdifficult to suppress coma aberration and other various aberrations.Meanwhile, it is preferable to set the lower limit value of theconditional expression (4) to 0.70, further preferable to 0.80, andfurthermore preferable to 0.90.

In the variable magnification optical system according to the presentembodiment, it is desirable that the following conditional expression(5) is satisfied:

2.00<D1Mw/fw<4.00  (5)

where D1Mw denotes a distance along the optical axis between the firstlens group and the first intermediate lens group in the wide angle endstate, and fw denotes the focal length of the variable magnificationoptical system in the wide angle end state.

The conditional expression (5) defines a ratio of the distance along theoptical axis between the first lens group and the first intermediatelens group in the wide angle end state to the focal length of thevariable magnification optical system in the wide angle end state.

With satisfying the conditional expression (5), the variablemagnification optical system according to the present embodiment caneffectively correct coma aberration and other various aberrations in thewide angle end state without making the size of a lens barrel large.

When the value of D1Mw/fw is equal to or exceeds the upper limit valueof the conditional expression (5) of the variable magnification opticalsystem according to the present embodiment, the distance along theoptical axis between the first lens group and the first intermediatelens group in the wide angle end state, becomes large, and thereby thesize of the lens barrel becomes large. Meanwhile, it is preferable toset the upper limit value of the conditional expression (5) to 3.90 andfurther preferable to 3.80.

On the other hand, when the value of D1Mw/fw in the conditionalexpression (5) of the variable magnification optical system according tothe present embodiment, is equal to or falls below the lower limitvalue, the distance along the optical axis between the first lens groupand the first intermediate lens group in the wide angle end state,becomes small, and it becomes difficult to correct effectively comaaberration and other various aberrations in the wide angle end state.Meanwhile, it is preferable to set the lower limit value of theconditional expression (5) to 2.10, and further preferable to 2.20.

In the variable magnification optical system according to the presentembodiment, it is desirable that the following conditional expression(6) is satisfied:

2.00<νM1P/νM1N<3.00  (6)

where νM1P denotes an Abbe's number of a lens having a strongestpositive refractive power in the first intermediate lens group, and νM1Ndenotes an Abbe's number of a lens having a strongest negativerefractive power in the first intermediate lens group.

The conditional expression (6) defines a ratio of the Abbe's number ofthe lens having the strongest positive refractive power in the firstintermediate lens group to the Abbe's number of the lens having thestrongest negative refractive power in the first intermediate lensgroup. With satisfying the conditional expression (6), the variablemagnification optical system according to the present embodiment cancorrect effectively chromatic aberration.

When the value of νM1P/νM1N is equal to or exceeds the upper limit valueof the conditional expression (6) of the variable magnification opticalsystem according to the present embodiment, the Abbe's number of thelens having the strongest negative refractive power in the firstintermediate lens group, becomes small, and thereby correction ofchromatic aberration becomes excessive. Meanwhile, it is preferable toset the upper limit value of the conditional expression (6) to 2.95,further preferable to 2.90 and furthermore preferable to 2.85.

On the other hand, when the value of νM1P/νM1N in the conditionalexpression (6) of the variable magnification optical system according tothe present embodiment, is equal to or falls below the lower limitvalue, the Abbe's number of the lens having the strongest positiverefractive power in the first intermediate lens group becomes small andgeneration of the chromatic aberration becomes excessive, thereby itbecoming difficult to correct it.

Meanwhile, it is preferable to set the lower limit value of theconditional expression (6) to 2.05, further preferable to 2.10 andfurthermore preferable to 2.15.

In the variable magnification optical system according to the presentembodiment, it is desirable that the following conditional expression(7) is satisfied:

0.20<fM1P/fM1N<0.80  (7)

where fM1P denotes a focal length of a lens having a strongest positiverefractive power in the first intermediate lens group, and fM1N denotesa focal length of a lens having a strongest negative refractive power inthe first intermediate lens group.

The conditional expression (7) defines a ratio of the focal length ofthe lens having the strongest positive refractive power in the firstintermediate lens group to the focal length of the lens having thestrongest negative refractive power in the first intermediate lensgroup. With satisfying the conditional expression (7), the variablemagnification optical system according to the present embodiment cancorrect effectively spherical aberration and other various aberrations.

When the value of fM1P/fM1N is equal to or exceeds the upper limit valueof the conditional expression (7) of the variable magnification opticalsystem according to the present embodiment, refractive power of the lenshaving the strongest negative refractive power in the first intermediatelens group, becomes strong, and thereby correction of sphericalaberration becomes excessive. Meanwhile, it is preferable to set theupper limit value of the conditional expression (7) to 0.75, and furtherpreferable to set it to 0.70.

On the other hand, when the value of fM1P/fM1N in the conditionalexpression (7) of the variable magnification optical system according tothe present embodiment, is equal to or falls below the lower limitvalue, refractive power of the lens having the strongest positiverefractive power in the first intermediate lens group becomes strong andgeneration of the spherical aberration becomes excessive, thereby itbecoming difficult to correct it. Meanwhile, it is preferable to set thelower limit value of the conditional expression (7) to 0.25, and furtherpreferable to set it to 0.30.

In the variable magnification optical system according to the presentembodiment, it is desirable that the following conditional expression(8) is satisfied:

38.00°<ωw<85.00°  (8)

where ωw denotes a half angle of view of the variable magnificationoptical system in the wide angle end state.

The conditional expression (8) defines a condition defining an optimalvalue of the angle of view in the wide angle end state. With satisfyingthe conditional expression (8), the variable magnification opticalsystem according to the present embodiment can correct superbly variousaberrations such as coma aberration, distortion, and curvature of field,while having wide angle of view.

It is preferable to set the upper limit value of the conditionalexpression (8) to 84.00° in order to make the effect of the presentembodiment secure.

In order to make the effect of the present embodiment secure, it ispreferable to set the lower limit value of the conditional expression(8) to 39.00°, further to 40. 00°, and furthermore to 41.00°.

In the variable magnification optical system according to the presentembodiment, it is desirable that the focusing lens group is composed ofone or two lenses. With this configuration, the focusing lens group maybe downsized and made light in weight.

Further, in the variable magnification optical system according to thepresent embodiment, it is desirable that the first intermediate lensgroup comprises at least two lens components having negative refractivepower. With this configuration, it is possible to correct effectivelyspherical aberration and chromatic aberration in the telephoto endstate.

Further, in the variable magnification optical system according to thepresent embodiment, it is desirable that the first lens group iscomposed of two lens components. With this configuration, even ifmanufacturing error occurs, mass productivity can be attained.

Further, in the variable magnification optical system according to thepresent embodiment, it is desirable that the rear lens group includes atleast one lens component at an image side of a most image side focusinglens group in the focusing lens groups. With this configuration, it ispossible to suppress variation in coma aberration occurring uponconducting focusing from an infinitely distant object to a close distantobject. Meanwhile, a single lens or a cemented lens is meant by the term“lens component” in the present specification.

In the variable magnification optical system according to the presentembodiment, it is desirable that at least one of the focusing lensgroups has positive refractive power. With this configuration,variations in spherical aberration and other various aberrations causedupon conducting focusing from an infinitely distant object to a closedistance object, can be suppressed.

Further, in the variable magnification optical system according to thepresent embodiment, it is desirable that the first intermediate lensgroup comprises, in order from the object side, a second lens grouphaving positive refractive power and a third lens group having positiverefractive power. With this configuration, variations in sphericalaberration and other various aberrations caused upon varyingmagnification from the wide angle end state to the telephoto end state,can be suppressed.

Further, in the variable magnification optical system according to thepresent embodiment, it is desirable that the rear lens group comprisesat least two focusing lens groups. With this configuration, variationsin spherical aberration and other various aberrations caused uponconducting focusing from an infinitely distant object to a closedistance object, can be suppressed effectively.

Further, an optical apparatus of the present embodiment is equipped withthe variable magnification optical system having the above describedconfiguration, so it is possible to realize an optical apparatus whichhas superb optical performance and in which the focusing lens group ismade light in weight.

Further, a method for manufacturing a variable magnification opticalsystem according to the present embodiment, is a method formanufacturing a variable magnification optical system which comprises,in order from an object side, a first lens group having negativerefractive power, a first intermediate lens group having positiverefractive power, a second intermediate lens group having negativerefractive power and a rear lens group, comprising the steps of:

constructing such that, upon varying a magnification from a wide angleend state to a telephoto end state, a distance between said first lensgroup and said first intermediate lens group is varied, a distancebetween said first intermediate lens group and said second intermediatelens group is varied, and a distance between said second intermediatelens group and said rear lens group is varied;

constructing such that said rear lens group comprises at least onefocusing lens group which is moved upon carrying out focusing from aninfinite distance object to a close distance object; and

constructing such that the following conditional expressions (1) and (2)are satisfied:

0.40<(−f1)/f1Rw<2.00  (1)

0.10<BFw/fw<1.00  (2)

where f1 denotes a focal length of said first lens group, f1Rw denotes acomposite focal length of all lens groups behind said first lens groupin the wide angle end state, BFw denotes a back focus of said variablemagnification optical system in the wide angle end state, and fw denotesa focal length of said variable magnification optical system in the wideangle end state.

Hereinafter, the variable magnification optical systems relating tonumerical examples of the present embodiment will be explained withreference to the accompanying drawings.

First Example

FIG. 1 is a sectional view of a variable magnification optical systemaccording to a First Example. Meanwhile, in FIG. 1 and FIG. 4, FIG. 7,FIG. 10, FIG. 13, FIG. 16, FIG. 19 and FIG. 22 described later, arrowsshow movement trajectories of the respective lens groups upon varyingmagnification from a wide angle end state (W) to a telephoto end state(T).

The variable magnification optical system according to the presentExample is composed of, in order from an object side, a first lens groupG1 having negative refractive power, a first intermediate lens group GM1having positive refractive power, an aperture stop S, a secondintermediate lens group GM2 having negative refractive power, and a rearlens group GR having positive refractive power.

The first intermediate lens group GM1 is composed of, in order from theobject side, a second lens group G2 having positive refractive power anda third lens group G3 having positive refractive power.

The second intermediate lens group GM2 is composed of a fourth lensgroup G4.

The rear lens group GR is composed of, in order from the object side, afifth lens group G5 having positive refractive power, a sixth lens groupG6 having positive refractive power, and a seventh lens group G7 havingnegative refractive power.

The first lens group G1 consists of, in order from the object side, anegative meniscus lens L11 having a convex surface facing the objectside, and a cemented negative lens constructed by a double concavenegative lens L12 cemented with a positive meniscus lens L13 having aconvex surface facing the object side.

The second lens group G2 consists of a cemented positive lensconstructed by a double convex positive lens L21 cemented with anegative meniscus lens L22 having a concave surface facing the objectside.

The third lens group G3 consists of a cemented positive lens constructedby a negative meniscus lens L31 having a convex surface facing theobject side cemented with a double convex positive lens L32.

The fourth lens group G4 consists of, in order from the object side, acemented negative lens constructed by a double concave negative lens L41cemented with a positive meniscus lens L42 having a convex surfacefacing the object side, and a positive meniscus lens L43 having a convexsurface facing the object side.

The fifth lens group G5 consists of a cemented positive lens constructedby a double convex positive lens L51 cemented with a negative meniscuslens L52 having a concave surface facing the object side.

The sixth lens group G6 consists of a double convex positive lens L61.

The seventh lens group G7 consists of a negative meniscus lens L71having a concave surface facing the object side.

In the variable magnification optical system according to the presentExample, upon varying magnification between the wide angle end state andthe telephoto end state, all lens groups of the first lens group G1 tothe seventh lens group G7 are moved along the optical axis such that adistance between the first lens group G1 and the second lens group G2, adistance between the second lens group G2 and the third lens group G3, adistance between the third lens group G3 and the fourth lens group G4, adistance between the fourth lens group G4 and the fifth lens group G5, adistance between the fifth lens group G5 and the sixth lens group G6 anda distance between the sixth lens group G6 and the seventh lens groupG7, are varied.

In the variable magnification optical system according to the presentExample, focusing from an infinite distance object to a close distanceobject is carried out by moving the fifth lens group G5 and the sixthlens group G6 independently from each other as respective focusing lensgroups.

Table 1 below shows various values of the variable magnification opticalsystem relating to the present Example.

In Table 1, “f” denotes a focal length, and “BF” denotes a back focus,that is, a distance along the optical axis from the most image side lenssurface to the image plane I.

In [Surface Data], “m” denotes an order of an optical surface countedfrom the object side, “r” denotes a radius of curvature, “d” denotes asurface-to-surface distance, that is, an interval from an n-th surfaceto an (n+1)-th surface, where n is an integer, “nd” denotes refractiveindex for d-line (wavelength λ=587.6 nm) and “νd” denotes an Abbe numberfor d-line (wavelength λ=587.6 nm). Further, “OP” denotes an objectsurface, “Variable” denotes a variable surface-to-surface distance, “S”denotes an aperture stop, and “I” denotes an image plane. Meanwhile,radius of curvature r=∞ denotes a plane surface, and refractive index ofthe air nd=1.00000 is omitted. In addition, a position of an asphericalsurface is expressed by attaching “*” to the surface number, and in thecolumn of the radius of curvature “r”, a paraxial radius of curvature isshown.

In [Aspherical Data], with respect to an aspherical surface shown in[Surface Data], an aspherical surface coefficient and a conicalcoefficient are shown in the case where the aspherical surface isexhibited by the following expression:

x=(h ² /r)/[1+{1−κ(h/r)²}^(1/2)]+A4h ⁴ +A6h ⁶ +A8h ⁸ +A10h ¹⁰

where “h” denotes a height in the direction perpendicular to the opticalaxis, “x” denotes a sag amount that is a distance along the optical axisfrom the tangent surface at the vertex of each aspherical surface at theheight “h”; “κ” denotes a conical coefficient; “A4”, “A6”, “A8” and“A10” denote respective aspherical coefficients, and “r” denotes aparaxial radius of curvature that is a radius of curvature of areference sphere. “E−n”, where n is an integer, denotes “×10^(−n)”, forexample, “1.234E-05” denotes “1.234×10⁻⁵”. Second order asphericalcoefficient “A2” is 0 and omitted.

In [Various Data], “FNO” denotes an F-number, “2ω” denotes an angle ofview (unit “*”), “Ymax” denotes a maximum image height, and “TL” denotesa total length of the variable magnification optical system according tothe present Example, that is, a distance along the optical axis from thefirst lens surface to the image plane I, and “dn” denotes a variabledistance from the n-th surface to the (n+1)-th surface. Meanwhile, “W”denotes a wide angle end state, “M” denotes an intermediate focal lengthstate, “T” denotes a tele photo end state, “INF” denotes time uponfocusing on an infinite distance object, and “CLO” denotes time uponfocusing on a close distance object.

In [Lens Group Data], a starting surface ST and a focal length f of eachlens group are shown.

In [Values for Conditional Expressions], values corresponding torespective conditional expressions of the variable magnification opticalsystem according to the present Example, are shown.

It is noted, here, that “mm” is generally used for the unit of lengthsuch as the focal length f, the radius of curvature r and the unit forother lengths shown in Table 1. However, since similar opticalperformance can be obtained by an optical system proportionally enlargedor reduced, the unit is not necessarily to be limited to “mm”.

Meanwhile, the explanation of reference symbols in Table 1 describedabove, is the same in Tables for the other Examples described hereinlater.

TABLE 1 First Example [Surface Data] m r d nd νd OP ∞ 1 270.0000 2.9001.74389 49.53 *2 33.2562 13.215  3 −1900.2102 2.100 1.59349 67.00 435.8236 7.700 2.00100 29.12 5 79.6938 Variable 6 271.3181 7.400 1.8348142.73 7 −36.9149 1.500 1.75520 27.57 8 −164.0000 Variable 9 39.75111.500 1.85000 27.03 10 25.6246 10.800  1.59319 67.90 11 −134.6401Variable 12(S) ∞ 2.350 13 −65.9523 1.300 1.80100 34.92 14 18.5797 4.7001.90366 31.27 15 51.6074 0.919 16 45.9293 2.500 1.94595 17.98 17120.0000 Variable 18 47.5350 7.100 1.48749 70.31 19 −24.2409 1.3001.69895 30.13 20 −74.7188 Variable 21 113.0000 4.200 1.58913 61.15 *22−108.0000 Variable *23 −30.5616 1.500 1.58913 61.15 24 −81.9388 BF I ∞[Aspherical Data] m: 2 K = 0.0000 A4 = 2.97162E−06 A6 = 1.62510E−09 A8 =2.42658E−13 A10 = 4.56491E−16 A12 = 8.02650E−19 m: 22 K = 1.0000 A4 =8.43912E−06 A6 = 6.68890E−10 A8 = 1.69267E−11 A10 = −5.36609E−14 m: 23 K= 1.0000 A4 = 8.13845E−06 A6 = −4.05875E−09 A8 = 1.66491E−11 A10 =−5.84964E−14 [Various Data] Variable magnification ratio 2.99 W M T f22.7 50.0 67.9 FNO 2.92 2.92 2.92 2ω 91.10 45.68 33.64 Ymax 19.32 21.6021.60 TL 188.45 157.95 163.95 BF 11.75 20.19 25.26 W M T W M T INF INFINF CLO CLO CLO d5 63.985 10.998 3.100 63.985 10.998 3.100 d8 1.0001.763 1.000 1.000 1.763 1.000 d11 1.900 12.973 26.707 1.900 12.97326.707 d17 20.431 12.752 12.052 20.013 11.839 10.654 d20 8.701 16.48016.780 8.112 16.125 16.831 d22 7.699 9.815 6.069 8.705 11.084 7.415[Lens Group Data] Group ST f 1 1 −46.132 2 6 102.733 3 9 64.434 4 12−89.031 5 18 92.237 6 21 94.399 7 23 −83.639 [Values for ConditionalExpressions] (1) (−f1)/f1Rw = 0.994 (2) BFw/fw = 0.518 (3) |fF|/ft =1.358 (4) f1N/f1 = 1.111 (5) D1Mw/fw = 2.819 (6) νM1P/νM1N = 2.463 (7)fM1P/fM1N = 0.587 (8) ωw = 45.55°

FIGS. 2A, 2B and 2C are graphs showing various aberrations upon focusingon an infinite distance object, respectively, in the wide angle endstate, in the intermediate focal length state and in the telephoto endstate, of the variable magnification optical system according to theFirst Example.

FIGS. 3A, 3B and 3C are graphs showing various aberrations upon focusingon a close distance object, respectively, in the wide angle end state,in the intermediate focal length state and in the telephoto end state,of the variable magnification optical system according to the FirstExample.

In the graphs showing aberrations as drawn in FIG. 2 and FIG. 3, “FNO”denotes an F-number, “NA” denotes a numerical aperture, and “Y” denotesan image height. In graphs showing spherical aberration, the value ofthe numerical aperture or F-number corresponding to the maximum apertureis shown. In graphs showing astigmatism and distortion, the maximumvalue of the image height is shown. In graphs showing coma aberration,the value for each image height is shown. “d” denotes d-line (wavelengthλ=587.6 nm), and “g” denotes g-line (wavelength λ=435.8 nm). In graphsshowing astigmatism, a solid line indicates a sagittal image plane, anda broken line indicates a meridional image plane. Meanwhile, in graphsshowing various aberrations in the other Examples as described below,the same symbols as in the present Example are employed.

As is apparent from the above-mentioned graphs showing variousaberrations, the variable magnification optical system relating to thepresent Example can correct superbly various aberrations over the wideangle end state to the telephoto end state and has excellent imagingperformance, and further has excellent imaging performance even uponfocusing on a close distance object.

Second Example

FIG. 4 is a sectional view of a variable magnification optical systemaccording to a Second Example of the present application.

The variable magnification optical system according to the presentExample is composed of, in order from an object side, a first lens groupG1 having negative refractive power, a first intermediate lens group GM1having positive refractive power, an aperture stop S, a secondintermediate lens group GM2 having negative refractive power, and a rearlens group GR having positive refractive power.

The first intermediate lens group GM1 is composed of, in order from theobject side, a second lens group G2 having positive refractive power anda third lens group G3 having positive refractive power.

The second intermediate lens group GM2 is composed of a fourth lensgroup G4.

The rear lens group GR is composed of, in order from the object side, afifth lens group G5 having positive refractive power, a sixth lens groupG6 having negative refractive power, and a seventh lens group G7 havingpositive refractive power.

The first lens group G1 consists of, in order from the object side, anegative meniscus lens L11 having a convex surface facing the objectside, and a cemented positive lens constructed by a double concavenegative lens L12 cemented with a positive meniscus lens L13 having aconvex surface facing the object side.

The second lens group G2 consists of a cemented positive lensconstructed by a double convex positive lens L21 cemented with anegative meniscus lens L22 having a concave surface facing the objectside.

The third lens group G3 consists of a cemented positive lens constructedby a negative meniscus lens L31 having a convex surface facing theobject side cemented with a double convex positive lens L32.

The fourth lens group G4 consists of, in order from the object side, adouble concave negative lens L41 and a cemented positive lensconstructed by a negative meniscus lens L42 having a convex surfacefacing the object side cemented with a double convex positive lens L43.

The fifth lens group G5 consists of a cemented positive lens constructedby a negative meniscus lens L51 having a convex surface facing theobject side cemented with a double convex positive lens L52.

The sixth lens group G6 consists of, in order from the object side, adouble convex positive lens L61 and a double concave negative lens L62.

The seventh lens group G7 consists of a positive meniscus lens L71having a convex surface facing the object side.

In the variable magnification optical system according to the presentExample, upon varying magnification between the wide angle end state andthe telephoto end state, all lens groups of the first lens group G1 tothe seventh lens group G7 are moved along the optical axis such that adistance between the first lens group G1 and the second lens group G2, adistance between the second lens group G2 and the third lens group G3, adistance between the third lens group G3 and the fourth lens group G4, adistance between the fourth lens group G4 and the fifth lens group G5, adistance between the fifth lens group G5 and the sixth lens group G6 anda distance between the sixth lens group G6 and the seventh lens groupG7, are varied.

In the variable magnification optical system according to the presentExample, focusing from an infinite distance object to a close distanceobject is carried out by moving the sixth lens group G6 toward the imageplane as focusing lens group.

Table 2 below shows various values of the variable magnification opticalsystem relating to the present Example.

TABLE 2 Second Example [Surface Data] m r d nd νd OP ∞ 1 199.9946 2.9001.74389 49.53 *2 27.7434 15.922  *3 −285.3676 2.100 1.67798 54.89 450.5985 6.605 2.00100 29.14 5 262.0850 Variable 6 93.3673 4.795 1.8348142.73 7 −123.3006 1.500 1.80518 25.45 8 −254.1381 Variable 9 40.59271.500 1.79504 28.69 10 25.0002 10.749  1.60300 65.44 11 −105.9135Variable 12(S) ∞ 2.540 13 −52.6667 1.300 1.85026 32.35 14 33.3539 4.58615 37.2026 1.300 1.74950 35.25 16 25.3810 5.571 1.80809 22.74 17−234.9670 Variable 18 62.4943 1.300 1.80518 25.45 19 18.1697 8.2001.55332 71.68 *20 −42.1612 Variable *21 −6257.4714 3.600 1.80301 25.5322 −49.3227 1.875 23 −33.3339 1.200 1.72825 28.38 24 70.6726 Variable 2547.6911 7.458 1.90200 25.26 26 110.0504 BF I ∞ [Aspherical Data] m: 2 κ= 0.0000 A4 = 3.47464E−06 A6 = 2.06289E−09 A8 = −2.87066E−12 A10 =6.84678E−15 A12 = −3.05130E−18 m: 3 κ = 1.0000 A4 = −3.34275E−07 A6 =−6.53686E−10 A8 = 1.41918E−12 A10 = −6.87012E−16 m: 20 κ = 1.0000 A4 =3.21231E−06 A6 = −2.72101E−08 A8 = 1.74184E−10 A10 = −4.74606E−13 m: 21κ = 1.0000 A4 = 4.04674E−06 A6 = −1.32981E−08 A8 = 1.27233E−10 A10 =−1.86784E−13 [Various Data] Variable magnification ratio 2.99 W M T f22.7 50.0 67.9 FNO 2.92 2.92 2.92 2ω 90.12 47.98 35.62 Ymax 19.31 21.6021.60 TL 199.49 166.47 170.49 BF 16.69 24.96 25.26 W M T W M T INF INFINF CLO CLO CLO d5 64.992 11.651 2.111 64.992 11.651 2.111 d8 7.9381.000 1.000 7.938 1.000 1.000 d11 2.500 9.805 17.785 2.500 9.805 17.785d17 8.103 6.811 2.000 8.103 6.811 2.000 d20 2.000 4.908 2.763 2.9246.260 4.220 d24 12.267 22.329 34.572 11.343 20.977 33.114 [Lens GroupData] Group ST f 1 1 −43.850 2 6 81.660 3 9 58.238 4 12 −95.001 5 1881.887 6 21 −66.376 7 25 88.300 [Values for Conditional Expressions] (1)(−f1)/f1Rw = 0.800 (2) BFw/fw = 0.735 (3) |fF|/ft = 0.978 (4) f1N/f1 =0.995 (5) D1Mw/fw = 2.863 (6) νM1P/νM1N = 2.281 (7) fM1P/fM1N = 0.405(8) ωw = 45.56°

FIG. 5A, FIG. 5B and FIG. 5C are graphs showing various aberrations uponfocusing on an infinite distance object, respectively, in the wide angleend state, in the intermediate focal length state and in the telephotoend state, of the variable magnification optical system according to theSecond Example.

FIG. 6A, FIG. 6B and FIG. 6C are graphs showing various aberrations uponfocusing on a close distance object, respectively, in the wide angle endstate, in the intermediate focal length state and in the telephoto endstate, of the variable magnification optical system according to theSecond Example.

As is apparent from the above-mentioned graphs showing variousaberrations, the variable magnification optical system relating to thepresent Example can correct superbly various aberrations over the wideangle end state to the telephoto end state and has excellent imagingperformance, and further has excellent imaging performance even uponfocusing on a close distance object.

Third Example

FIG. 7 is a sectional view of a variable magnification optical systemaccording to a Third Example of the present application.

The variable magnification optical system according to the presentExample is composed of, in order from an object side, a first lens groupG1 having negative refractive power, a first intermediate lens group GM1having positive refractive power, an aperture stop S, a secondintermediate lens group GM2 having negative refractive power, and a rearlens group GR having positive refractive power.

The first intermediate lens group GM1 is composed of, in order from theobject side, a second lens group G2 having positive refractive power anda third lens group G3 having positive refractive power.

The second intermediate lens group GM2 is composed of a fourth lensgroup G4.

The rear lens group GR is composed of, in order from the object side, afifth lens group G5 having positive refractive power, a sixth lens groupG6 having positive refractive power, and a seventh lens group G7 havingnegative refractive power.

The first lens group G1 consists of, in order from the object side, anegative meniscus lens L11 having a convex surface facing the objectside, and a cemented negative lens constructed by a double concavenegative lens L12 cemented with a positive meniscus lens L13 having aconvex surface facing the object side.

The second lens group G2 consists of a cemented positive lensconstructed by a double convex positive lens L21 cemented with anegative meniscus lens L22 having a concave surface facing the objectside.

The third lens group G3 consists of a cemented positive lens constructedby a negative meniscus lens L31 having a convex surface facing theobject side cemented with a double convex positive lens L32.

The fourth lens group G4 consists of, in order from the object side, adouble concave negative lens L41 and a cemented negative lensconstructed by a double concave negative lens L42 cemented with a doubleconvex positive lens L43.

The fifth lens group G5 consists of a cemented positive lens constructedby a negative meniscus lens L51 having a convex surface facing theobject side cemented with a double convex positive lens L52.

The sixth lens group G6 consists of a double convex positive lens L61.

The seventh lens group G7 is composed of, in order from the object side,a positive meniscus lens L71 having a concave surface facing the objectside and a double concave negative lens L72.

In the variable magnification optical system according to the presentExample, upon varying magnification between the wide angle end state andthe telephoto end state, all lens groups of the first lens group G1 tothe seventh lens group G7 are moved along the optical axis such that adistance between the first lens group G1 and the second lens group G2, adistance between the second lens group G2 and the third lens group G3, adistance between the third lens group G3 and the fourth lens group G4, adistance between the fourth lens group G4 and the fifth lens group G5, adistance between the fifth lens group G5 and the sixth lens group G6 anda distance between the sixth lens group G6 and the seventh lens groupG7, are varied.

In the variable magnification optical system according to the presentExample, focusing from an infinite distance object to a close distanceobject is carried out by moving the sixth lens group G6 along theoptical axis toward the object as focusing lens group.

Table 3 below shows various values of the variable magnification opticalsystem relating to the present Example.

TABLE 3 Third Example [Surface Data] m r d nd νd OP ∞ 1 200.0000 2.9001.74389 49.53 *2 29.9416 15.494  *3 −200.8674 2.100 1.69343 53.30 444.6733 7.746 1.85000 27.03 5 318.4789 Variable 6 108.1956 5.825 1.8040046.60 7 −62.4397 1.500 1.84666 23.80 8 −135.1571 Variable 9 39.61941.500 1.84666 23.80 10 27.1969 9.538 1.60300 65.44 11 −223.7185 Variable12 (S) ∞ 2.115 13 −77.7324 1.300 1.83481 42.73 14 186.4173 1.924 15−51.8167 1.300 1.80100 34.92 16 27.4630 5.440 1.80809 22.74 17 −78.0293Variable 18 273.2433 1.500 1.95000 29.37 19 29.6710 6.516 1.59319 67.9020 −41.4738 Variable 21 39.0977 6.500 1.48749 70.31 22 −208.2456Variable *23 −736.4795 8.500 1.55332 71.67 24 −42.9142 6.153 25 −34.63671.500 1.67798 54.89 *26 147.0962 BF I ∞ [Aspherical Data] m: 2 κ =0.0000 A4 =  2.64488E−06 A6 =  7.93387E−10 A8 = −2.18796E−13 A10 = 2.18394E−15 A12 = −6.34900E−19 m: 3 κ = 1.0000 A4 = −2.63676E−07 A6 =−4.45738E−10 A8 =  9.61010E−13 A10 = −3.72624E−16 m: 23 κ = 1.0000 A4 =−2.62769E−07 A6 =  7.24281E−10 A8 = −9.63646E−13 A10 = −6.01683E−15 m:26 κ = 1.0000 A4 =  5.86678E−07 A6 =  1.11104E−09 A8 =  1.08716E−11 A10= −2.05060E−14 [Various Data] Variable magnification ratio 2.99 W M T f22.7 50.0 67.9 FNO 2.92 2.92 2.92 2ω 90.26 47.38 35.28 Ymax 19.64 21.6021.60 TL 204.49 174.12 175.49 BF 16.69 28.18 36.33 W M T W M T INF INFINF CLO CLO CLO d5 59.091 10.830 2.000 59.091 10.830 2.000 d8 13.3281.000 1.000 13.328 1.000 1.000 d11 2.500 14.191 22.877 2.500 14.19122.877 d17 9.032 7.248 2.000 9.032 7.248 2.000 d20 12.353 19.355 19.92411.550 18.113 18.492 d22 2.147 3.969 2.006 2.949 5.211 3.438 [Lens GroupData] Group ST f 1 1 −40.605 2 6 77.859 3 9 66.608 4 12 −52.441 5 18160.100 6 21 68.111 7 23 −97.113 [Values for Conditional Expressions](1) (−f1)/f1Rw = 0.801 (2) BFw/fw = 0.735 (3) |fF|/ft = 1.003 (4) f1N/f1= 1.174 (5) D1Mw/fw = 2.603 (6) νM1P/νM1N = 2.750 (7) fM1P/fM1N = 0.376(8) ωw = 45.13°

FIG. 8A, FIG. 8B and FIG. 8C are graphs showing various aberrations uponfocusing on an infinite distance object, respectively, in the wide angleend state, in the intermediate focal length state and in the telephotoend state, of the variable magnification optical system according to theThird Example.

FIGS. 9A, 9B and 9C are graphs showing various aberrations upon focusingon a close distance object, respectively, in the wide angle end state,in the intermediate focal length state and in the telephoto end state,of the variable magnification optical system according to the ThirdExample.

As is apparent from the above-mentioned graphs showing variousaberrations, the variable magnification optical system relating to thepresent Example can correct superbly various aberrations over the wideangle end state to the telephoto end state and has excellent imagingperformance, and further has excellent imaging performance even uponfocusing on a close distance object.

Fourth Example

FIG. 10 is a sectional view of a variable magnification optical systemaccording to a Fourth Example of the present application.

The variable magnification optical system according to the presentExample is composed of, in order from an object side, a first lens groupG1 having negative refractive power, a first intermediate lens group GM1having positive refractive power, an aperture stop S, a secondintermediate lens group GM2 having negative refractive power, and a rearlens group GR having positive refractive power.

The first intermediate lens group GM1 is composed of a second lens groupG2 having positive refractive power.

The second intermediate lens group GM2 is composed of a third lens groupG3.

The rear lens group GR is composed of, in order from the object side, afourth lens group G4 having positive refractive power and a fifth lensgroup G5 having negative refractive power.

The first lens group G1 consists of, in order from the object side, anegative meniscus lens L11 having a convex surface facing the objectside, and a cemented positive lens constructed by a negative meniscuslens L12 having a convex surface facing the object side cemented with apositive meniscus lens L13 having a convex surface facing the objectside.

The second lens group G2 consists of, in order from the object side, acemented positive lens constructed by a double convex positive lens L21cemented with a negative meniscus lens L22 having a concave surfacefacing the object side, and a cemented positive lens constructed by anegative meniscus lens L23 having a convex surface facing the objectside cemented with a double convex positive lens L24.

The third lens group G3 consists of, in order from the object side, adouble concave negative lens L31, a cemented positive lens constructedby a negative meniscus lens L32 having a convex surface facing theobject side cemented with a double convex positive lens L33, and acemented positive lens constructed by a negative meniscus lens L34having a convex surface facing the object side cemented with a doubleconvex positive lens L35.

The fourth lens group G4 consists of a double convex positive lens L41.

The fifth lens group G5 consists of, in order from the object side, apositive meniscus lens L51 having a concave surface facing the objectside and a negative meniscus lens L52 having a concave surface facingthe object side.

In the variable magnification optical system according to the presentExample, upon varying magnification between the wide angle end state andthe telephoto end state, all lens groups of the first lens group G1 tothe fifth lens group G5 are moved along the optical axis such that adistance between the first lens group G1 and the second lens group G2, adistance between the second lens group G2 and the third lens group G3, adistance between the third lens group G3 and the fourth lens group G4,and a distance between the fourth lens group G4 and the fifth lens groupG5, are varied.

In the variable magnification optical system according to the presentExample, focusing from an infinite distance object to a close distanceobject is carried out by moving the fourth lens group G4 toward theobject as a focusing lens group.

Table 4 below shows various values of the variable magnification opticalsystem relating to the present Example.

TABLE 4 Fourth Example [Surface Data] m r d nd νd OP ∞ 1 200.0000 2.9001.74389 49.53 *2 27.7802 14.448  *3 1296.6773 2.100 1.69343 53.30 434.8575 9.043 1.85000 27.03 5 174.0595 Variable 6 96.7860 6.874 1.8040046.60 7 −52.4305 1.500 1.84666 23.80 8 −177.3376 1.000 9 43.5282 1.5001.84666 23.80 10 26.9388 11.032  1.59319 67.90 11 −99.1173 Variable 12(S) ∞ 2.808 13 −44.3650 1.300 1.80400 46.60 14 71.1308 1.016 15 416.39081.300 1.71999 50.27 16 23.6979 5.430 1.80809 22.74 17 −136.8595 7.916 182542.1309 1.500 1.90200 25.26 19 30.4377 6.844 1.59319 67.90 20 −35.3418Variable 21 43.9437 6.500 1.48749 70.32 22 −380.1806 Variable *23−107.1075 8.500 1.55332 71.68 24 −86.8745 7.112 25 −22.8630 1.5001.67798 54.89 *26 −40.7153 BF I ∞ [Aspherical Data] m: 2 κ = 0.0000 A4 = 3.03915E−06 A6 =  2.46295E−09 A8 = −2.53532E−12 A10 =  3.74583E−15 A12= −6.34900E−19 m: 3 κ = 1.0000 A4 = −2.78528E−07 A6 = −3.14446E−10 A8 = 3.58529E−13 A10 = −1.27209E−16 m: 23 κ = 1.0000 A4 =  6.52833E−06 A6 = 1.33655E−08 A8 = −7.01957E−12 A10 =  5.45626E−14 m: 26 κ = 1.0000 A4 =−2.26773E−06 A6 = −1.49552E−09 A8 =  2.69475E−11 A10 = −3.21917E−14[Various Data] Variable magnification ratio 2.99 W M T f 22.7 50.0 67.9FNO 2.92 2.92 2.92 2ω 90.80 48.02 35.28 Ymax 19.27 21.60 21.60 TL 199.61181.30 175.49 BF 13.71 19.42 30.99 W M T W M T INF INF INF CLO CLO CLOd5 64.761 16.002 3.958 64.761 16.002 3.958 d11 2.500 10.994 21.579 2.50010.994 21.579 d20 12.355 28.806 14.836 11.534 27.309 13.300 d22 4.1723.955 2.000 4.993 5.453 3.536 [Lens Group Data] Group ST f 1 1 −43.293 26 37.710 3 12 −166.903 4 21 81.211 5 23 −87.491 [Values for ConditionalExpressions] (1) (−f1)/f1Rw = 0.913 (2) BFw/fw = 0.604 (3) |fF|/ft =1.196 (4) f1N/f1 = 1.009 (5) D1Mw/fw = 2.853 (6) νM1P/νM1N = 2.853 (7)fM1P/fM1N = 0.424 (8) ωw = 45.40°

FIG. 11A, FIG. 11B and FIG. 11C are graphs showing various aberrationsupon focusing on an infinite distance object, respectively, in the wideangle end state, in the intermediate focal length state and in thetelephoto end state, of the variable magnification optical systemaccording to the Fourth Example.

FIG. 12A, FIG. 12B and FIG. 12C are graphs showing various aberrationsupon focusing on a close distance object, respectively, in the wideangle end state, in the intermediate focal length state and in thetelephoto end state, of the variable magnification optical systemaccording to the Fourth Example.

As is apparent from the above-mentioned graphs showing variousaberrations, the variable magnification optical system relating to thepresent Example can correct superbly various aberrations over the wideangle end state to the telephoto end state and has excellent imagingperformance, and further has excellent imaging performance even uponfocusing on a close distance object.

Fifth Example

FIG. 13 is a sectional view of a variable magnification optical systemaccording to a Fifth Example of the present application.

The variable magnification optical system according to the presentExample is composed of, in order from an object side, a first lens groupG1 having negative refractive power, a first intermediate lens group GM1having positive refractive power, an aperture stop S, a secondintermediate lens group GM2 having negative refractive power, and a rearlens group GR having positive refractive power.

The first intermediate lens group GM1 is composed of a second lens groupG2 having positive refractive power.

The second intermediate lens group GM2 is composed of a third lens groupG3.

The rear lens group GR is composed of, in order from the object side, afourth lens group G4 having positive refractive power, a fifth lensgroup G5 having positive refractive power and a sixth lens group G6having negative refractive power.

The first lens group G1 consists of, in order from the object side, anegative meniscus lens L11 having a convex surface facing the objectside, and a cemented negative lens constructed by a negative meniscuslens L12 having a convex surface facing the object side cemented with apositive meniscus lens L13 having a convex surface facing the objectside.

The second lens group G2 consists of, in order from the object side, acemented positive lens constructed by a double convex positive lens L21cemented with a negative meniscus lens L22 having a concave surfacefacing the object side, and a cemented positive lens constructed by anegative meniscus lens L23 having a convex surface facing the objectside cemented with a double convex positive lens L24.

The third lens group G3 consists of, in order from the object side, adouble concave negative lens L31, and a cemented positive lensconstructed by a double concave negative lens L32 cemented with a doubleconvex positive lens L33.

The fourth lens group G4 consists of a cemented positive lensconstructed by a double convex positive lens L41 cemented with anegative meniscus lens L42 having a concave surface facing the objectside.

The fifth lens group G5 consists of a double convex positive lens L51.

The sixth lens group G6 consists of a negative meniscus lens L61 havinga concave surface facing the object side.

In the variable magnification optical system according to the presentExample, upon varying magnification between the wide angle end state andthe telephoto end state, all lens groups of the first lens group G1 tothe sixth lens group G6 are moved along the optical axis such that adistance between the first lens group G1 and the second lens group G2, adistance between the second lens group G2 and the third lens group G3, adistance between the third lens group G3 and the fourth lens group G4, adistance between the fourth lens group G4 and the fifth lens group G5,and a distance between the fifth lens group G5 and the sixth lens groupG6, are varied.

In the variable magnification optical system according to the presentExample, focusing from an infinite distance object to a close distanceobject is carried out by moving the fourth lens group G4 and the fifthlens group G5 independently toward the object as respective focusinglens groups.

Table 5 below shows various values of the variable magnification opticalsystem relating to the present Example.

TABLE 5 Fifth Example [Surface Data] m r d nd νd OP ∞ 1 217.2239 2.9001.74389 49.53 *2 30.2414 13.112  3 1223.5572 2.100 1.59349 67.00 435.8181 6.436 2.00069 25.46 5 72.5839 Variable 6 128.9112 7.447 1.8160046.59 7 −39.6982 1.500 1.85000 27.03 8 −142.9408 1.000 9 40.8283 1.5001.80518 25.45 10 25.0719 10.948  1.60300 65.44 11 −92.3055 Variable 12(S) ∞ 2.486 13 −55.5201 1.300 1.90265 35.72 14 121.6217 1.190 15−124.4061 1.300 1.67270 32.18 16 22.4038 6.400 1.80809 22.74 17 −97.2368Variable 18 62.1388 6.900 1.48749 70.32 19 −23.2151 1.300 1.78472 25.6420 −50.9732 Variable 21 186.2633 4.200 1.58913 61.15 *22 −79.5614Variable *23 −33.8149 1.500 1.58913 61.15 24 −131.2649 BF I ∞[Aspherical Surface Data] m: 2 κ = 0.0000 A4 = 3.46899E−06 A6 =3.81982E−09 A8 = −6.40834E−12  A10 = 1.09738E−14 A12 = −4.82160E−18  m:22 κ = 1.0000 A4 = 6.88818E−06 A6 = −6.09818E−10  A8 = 8.44660E−12 A10 =−2.63571E−14  m: 23 κ = 1.0000 A4 = 8.06346E−06 A6 = −8.60497E−09  A8 =2.28581E−11 A10 = −5.12367E−14  [Various Data] Variable magnificationratio 2.99 W M T f 22.7 50.0 67.9 FNO 2.92 2.92 2.92 2ω 91.24 45.9233.78 Ymax 19.34 21.60 21.60 TL 188.49 155.49 159.75 BF 16.19 19.6924.21 W M T W M T INF INF INF CLO CLO CLO d5 63.857 10.035 2.501 63.85710.035 2.501 d11 2.202 10.972 22.702 2.202 10.972 22.702 d17 19.52410.852 10.688 19.122 9.959 9.322 d20 8.007 19.445 19.346 7.507 19.08219.339 d22 5.193 10.974 6.787 6.095 12.231 8.161 [Lens Group Data] GroupST f 1 1 −42.007 2 6 36.073 3 12 −74.292 4 18 96.221 5 21 95.186 6 23−77.759 [Values for Conditional Expressions] (1) (−f1)/f1Rw = 0.882 (2)BFw/fw = 0.713 (3) |fF|/ft = 1.402 (4) f1N/f1 = 1.132 (5) D1Mw/fw =2.813 (6) νM1P/νM1N = 2.421 (7) fM1P/fM1N = 0.521 (8) ωw = 45.62°

FIG. 14A, FIG. 14B and FIG. 14C are graphs showing various aberrationsupon focusing on an infinite distance object, respectively, in the wideangle end state, in the intermediate focal length state and in thetelephoto end state, of the variable magnification optical systemaccording to the Fifth Example.

FIG. 15A, FIG. 15B and FIG. 15C are graphs showing various aberrationsupon focusing on a close distance object, respectively, in the wideangle end state, in the intermediate focal length state and in thetelephoto end state, of the variable magnification optical systemaccording to the Fifth Example.

As is apparent from the above-mentioned graphs showing variousaberrations, the variable magnification optical system relating to thepresent Example can correct superbly various aberrations over the wideangle end state to the telephoto end state and has excellent imagingperformance, and further has excellent imaging performance even uponfocusing on a close distance object.

Sixth Example

FIG. 16 is a sectional view of a variable magnification optical systemaccording to a Sixth Example of the present application.

The variable magnification optical system according to the presentExample is composed of, in order from an object side, a first lens groupG1 having negative refractive power, a first intermediate lens group GM1having positive refractive power, an aperture stop S, a secondintermediate lens group GM2 having negative refractive power, and a rearlens group GR having positive refractive power.

The first intermediate lens group GM1 is composed of, in order from theobject side, a second lens group G2 having positive refractive power anda third lens group G3 having positive refractive power.

The second intermediate lens group GM2 is composed of a fourth lensgroup G4.

The rear lens group GR is composed of, in order from the object side, afifth lens group G5 having positive refractive power, a sixth lens groupG6 having positive refractive power, and a seventh lens group G7 havingnegative refractive power.

The first lens group G1 consists of, in order from the object side, anegative meniscus lens L11 having a convex surface facing the objectside, and a cemented negative lens constructed by a negative meniscuslens L12 having a convex surface facing the object side cemented with apositive meniscus lens L13 having a convex surface facing the objectside.

The second lens group G2 consists of a cemented positive lensconstructed by a double convex positive lens L21 cemented with anegative meniscus lens L22 having a concave surface facing the object.

The third lens group G3 consists of a cemented positive lens constructedby a negative meniscus lens L31 having a convex surface facing theobject side cemented with a double convex positive lens L32.

The fourth lens group G4 consists of a cemented negative lensconstructed by a double concave negative lens L41 cemented with apositive meniscus lens L42 having a convex surface facing the objectside.

The fifth lens group G5 consists of a cemented positive lens constructedby a double convex positive lens L51 cemented with a negative meniscuslens L52 having a concave surface facing the object side.

The sixth lens group G6 consists of a double convex positive lens L61.

The seventh lens group G7 consists of a negative meniscus lens L71having a concave surface facing the object side.

In the variable magnification optical system according to the presentExample, upon varying magnification between the wide angle end state andthe telephoto end state, all lens groups of the first lens group G1 tothe seventh lens group G7 are moved along the optical axis such that adistance between the first lens group G1 and the second lens group G2, adistance between the second lens group G2 and the third lens group G3, adistance between the third lens group G3 and the fourth lens group G4, adistance between the fourth lens group G4 and the fifth lens group G5, adistance between the fifth lens group G5 and the sixth lens group G6 anda distance between the sixth lens group G6 and the seventh lens groupG7, are varied.

In the variable magnification optical system according to the presentExample, focusing from an infinite distance object to a close distanceobject is carried out by moving the fifth lens group G5 and the sixthlens group G6 along the optical axis independently toward the object asrespective focusing lens groups.

Table 6 below shows various values of the variable magnification opticalsystem relating to the present Example.

TABLE 6 Sixth Example [Surface Data] m r d nd νd OP ∞ 1 259.2015 2.9001.74389 49.53 *2 30.9799 13.410  3 1201.6909 2.100 1.59349 66.99 436.4155 6.936 2.00100 29.14 5 81.5436 Variable 6 124.3745 6.555 1.8040046.60 7 −55.7538 1.500 1.72825 28.38 8 −633.0468 Variable 9 44.96591.500 1.85000 27.03 10 27.3358 10.990  1.59319 67.90 11 −89.5168Variable 12 (S) ∞ 2.562 13 −58.2664 1.300 1.68893 31.16 14 20.8969 4.7421.80809 22.74 15 201.5296 Variable 16 52.2605 6.900 1.48749 70.31 17−26.1209 1.300 1.69895 30.13 18 −72.7540 Variable 19 130.0000 4.2001.58913 61.15 *20 −100.4826 Variable *21 −44.3630 1.500 1.58913 61.15 22−412.9422 BF I ∞ [Aspherical Surface Data] m: 2 κ = 0.0000 A4 =3.40299E−06 A6 = 1.78453E−09 A8 = −2.01869E−13  A10 = 1.07948E−15 A12 =2.74510E−19 m: 20 κ = 1.0000 A4 = 8.80591E−06 A6 = −1.07404E−09  A8 =1.74456E−11 A10 = −2.66494E−14  m: 21 κ = 1.0000 A4 = 6.66893E−06 A6 =−5.20154E−09  A8 = 5.00802E−12 A10 = −7.75803E−15  [Various Data]Variable magnification ratio 2.99 W M T f 22.7 50.0 67.9 FNO 2.92 2.922.92 2ω 91.30 45.88 33.64 Ymax 19.36 21.60 21.60 TLL 188.49 156.49165.34 BF 14.19 20.41 24.73 W M T W M T INF INF INF CLO CLO CLO d564.909 10.197 2.263 64.909 10.197 2.263 d8 1.000 1.000 1.000 1.000 1.0001.000 d11 2.200 12.573 28.831 2.200 12.573 28.831 d15 22.896 13.30411.893 22.388 12.281 10.318 d18 8.047 19.430 19.884 7.707 19.294 20.259d20 6.853 11.181 8.344 7.701 12.340 9.543 [Lens Group Data] Group ST f 11 −45.334 2 6 112.275 3 9 63.547 4 12 −98.234 5 16 92.914 6 19 96.856 721 −84.494 [Values for Conditional Expressions] (1) (−f1)/f1Rw = 0.954(2) BFw/fw = 0.625 (3) |fF|/ft = 1.368 (4) f1N/f1 = 1.049 (5) D1Mw/fw =2.859 (6) νM1P/νM1N = 2.393 (7) fM1P/fM1N = 0.435 (8) ωw = 45.65°

FIG. 17A, FIG. 17B and FIG. 17C are graphs showing various aberrationsupon focusing on an infinite distance object, respectively, in the wideangle end state, in the intermediate focal length state and in thetelephoto end state, of the variable magnification optical systemaccording to the Sixth Example.

FIG. 18A, FIG. 18B and FIG. 18C are graphs showing various aberrationsupon focusing on a close distance object, respectively, in the wideangle end state, in the intermediate focal length state and in thetelephoto end state, of the variable magnification optical systemaccording to the Sixth Example.

As is apparent from the above-mentioned graphs showing aberrations, thevariable magnification optical system relating to the present Examplecan correct superbly various aberrations over the wide angle end stateto the telephoto end state and has excellent imaging performance, andfurther has excellent imaging performance even upon focusing on a closedistance object.

Seventh Example

FIG. 19 is a sectional view of a variable magnification optical systemaccording to a Seventh Example of the present application.

The variable magnification optical system according to the presentExample is composed of, in order from an object side, a first lens groupG1 having negative refractive power, a first intermediate lens group GM1having positive refractive power, an aperture stop S, a secondintermediate lens group GM2 having negative refractive power, and a rearlens group GR having positive refractive power.

The first intermediate lens group GM1 is composed of a second lens groupG2 having positive refractive power.

The second intermediate lens group GM2 is composed of a third lens groupG3.

The rear lens group GR is composed of, in order from the object side, afourth lens group G4 having positive refractive power, a fifth lensgroup G5 having positive refractive power and a sixth lens group G6having negative refractive power.

The first lens group G1 consists of, in order from the object side, anegative meniscus lens L11 having a convex surface facing the objectside, and a cemented negative lens constructed by a double concavenegative lens L12 cemented with a positive meniscus lens L13 having aconvex surface facing the object side.

The second lens group G2 consists of, in order from the object side, acemented positive lens constructed by a double convex positive lens L21cemented with a negative meniscus lens L22 having a concave surfacefacing the object side, and a cemented positive lens constructed by anegative meniscus lens L23 having a convex surface facing the objectside cemented with a double convex positive lens L24.

The third lens group G3 consists of, in order from the object side, adouble concave negative lens L31, a cemented positive lens constructedby a negative meniscus lens L32 having a convex surface facing theobject side cemented with a double convex positive lens L33 and acemented positive lens constructed by a double concave negative lens L33cemented with a double convex positive lens L34.

The fourth lens group G4 consists of a double convex positive lens L41.

The fifth lens group G5 consists of a positive meniscus lens L51 havinga concave surface facing the object side.

The sixth lens group G6 consists of a negative meniscus lens L61 havinga concave surface facing the object side.

In the variable magnification optical system according to the presentExample, upon varying magnification between the wide angle end state andthe telephoto end state, all lens groups of the first lens group G1 tothe sixth lens group G6 are moved along the optical axis such that adistance between the first lens group G1 and the second lens group G2, adistance between the second lens group G2 and the third lens group G3, adistance between the third lens group G3 and the fourth lens group G4, adistance between the fourth lens group G4 and the fifth lens group G5,and a distance between the fifth lens group G5 and the sixth lens groupG6, are varied.

In the variable magnification optical system according to the presentExample, focusing from an infinite distance object to a close distanceobject is carried out by moving the fourth lens group G4 along theoptical axis toward the object as a focusing lens group.

Table 7 below shows various values of the variable magnification opticalsystem relating to the present Example.

TABLE 7 Seventh Example [Surface Data] m r d nd νd OP ∞ 1 200.0000 2.9001.74389 49.53 *2 28.4969 14.488  *3 −5398.0521 2.100 1.69343 53.30 436.6732 8.665 1.85000 27.03 5 187.9030 Variable 6 91.7611 6.648 1.8040046.60 7 −55.7166 1.500 1.84666 23.80 8 −203.7508 1.000 9 42.9517 1.5001.84666 23.80 10 26.9325 10.417  1.59319 67.90 11 −98.1277 Variable 12(S) ∞ 2.820 13 −45.5709 1.300 1.80400 46.60 14 57.2932 0.868 15 120.20071.300 1.71999 50.27 16 23.4150 5.485 1.80809 22.74 17 −181.7727 8.145 18−482.8882 1.500 1.90200 25.26 19 32.5158 6.892 1.59319 67.90 20 −35.1691Variable 21 47.0119 6.500 1.48749 70.32 22 −168.6086 Variable *23−111.3712 8.500 1.55332 71.68 24 −71.1538 Variable 25 −29.2568 1.5001.67798 54.89 *26 −86.3647 BF I ∞ [Aspherical Data] m: 2 κ = 0.0000 A4 =3.18150E−06 A6 = 1.29143E−09 A8 = −4.45637E−13  A10 = 2.21668E−15 A12 =−6.34900E−19  m: 3 κ = 1.0000 A4 = −1.73423E−07  A6 = −4.20289E−10  A8 =7.96941E−13 A10 = −4.23115E−16  m: 23 κ = 1.0000 A4 = 2.52053E−06 A6 =5.96196E−09 A8 = 1.22687E−12 A10 = −9.60903E−15  m: 26 κ = 1.0000 A4 =−3.00816E−06  A6 = 2.06736E−09 A8 = 2.50057E−11 A10 = −4.88231E−14 [Various Data] Variable magnification ratio 2.99 W M T f 22.7 50.0 67.9FNO 2.92 2.92 2.92 2ω 90.82 47.84 35.28 Ymax 19.42 21.60 21.60 TL 199.64180.36 175.49 BF 14.74 19.85 28.18 W M T W M T INF INF INF CLO CLO CLOd5 65.865 14.675 2.075 65.865 14.675 2.075 d11 2.500 9.999 19.897 2.5009.999 19.897 d20 12.261 28.219 17.697 11.472 26.839 16.195 d22 2.2393.776 2.000 3.027 5.155 3.503 d24 8.010 9.814 11.610 8.010 9.814 11.610[Lens Group Data] Group ST f 1 1 −43.315 2 6 37.392 3 12 −136.693 4 2176.163 5 23 331.174 6 25 −65.961 [Values for Conditional Expressions](1) (−f1)/f1Rw = 0.922 (2) BFw/fw = 0.649 (3) |fF|/ft = 1.122 (4) f1N/f1= 1.039 (5) D1Mw/fw = 2.902 (6) νM1P/νM1N = 2.853 (7) fM1P/fM1N = 0.413(8) ωw = 45.41°

FIG. 20A, FIG. 20B and FIG. 20C are graphs showing various aberrationsupon focusing on an infinite distance object, respectively, in the wideangle end state, in the intermediate focal length state and in thetelephoto end state, of the variable magnification optical systemaccording to the Seventh Example.

FIG. 21A, FIG. 21B and FIG. 21C are graphs showing various aberrationsupon focusing on a close distance object, respectively, in the wideangle end state, in the intermediate focal length state and in thetelephoto end state, of the variable magnification optical systemaccording to the Seventh Example.

As is apparent from the above-mentioned graphs showing variousaberrations, the variable magnification optical system relating to thepresent Example can correct superbly various aberrations over the wideangle end state to the telephoto end state and has excellent imagingperformance, and further has excellent imaging performance even uponfocusing on a close distance object.

Eighth Example

FIG. 22 is a sectional view of a variable magnification optical systemaccording to an Eighth Example of the present application.

The variable magnification optical system according to the presentExample is composed of, in order from an object side, a first lens groupG1 having negative refractive power, a first intermediate lens group GM1having positive refractive power, an aperture stop S, a secondintermediate lens group GM2 having negative refractive power, and a rearlens group GR having positive refractive power.

The first intermediate lens group GM1 is composed of a second lens groupG2 having positive refractive power.

The second intermediate lens group GM2 is composed of a third lens groupG3.

The rear lens group GR is composed of, in order from the object side, afourth lens group G4 having positive refractive power, a fifth lensgroup G5 having negative refractive power, a sixth lens group G6 havingpositive refractive power and a seventh lens group G7 having negativerefractive power.

The first lens group G1 consists of, in order from the object side, anegative meniscus lens L11 having a convex surface facing the objectside, and a cemented positive lens constructed by a negative meniscuslens L12 having a convex surface facing the object side cemented with apositive meniscus lens L13 having a convex surface facing the objectside.

The second lens group G2 consists of, in order from the object side, acemented positive lens constructed by a double convex positive lens L21cemented with a negative meniscus lens L22 having a concave surfacefacing the object side, and a cemented positive lens constructed by anegative meniscus lens L23 having a convex surface facing the objectside cemented with a double convex positive lens L24.

The third lens group G3 consists of, in order from the object side, anegative meniscus lens L31 having a concave surface facing the objectside, and a cemented positive lens constructed by a double concavenegative lens L32 cemented with a positive meniscus lens L33 having aconvex surface facing the object side.

The fourth lens group G4 consists of a double convex positive lens L41.

The fifth lens group G5 consists of a negative meniscus lens L51 havinga concave surface facing the object side.

The sixth lens group G6 consists of a double convex positive lens L61.

The seventh lens group G7 consists of a negative meniscus lens L71having a concave surface facing the object side.

In the variable magnification optical system according to the presentExample, upon varying magnification between the wide angle end state andthe telephoto end state, all lens groups of the first lens group G1 tothe seventh lens group G7 are moved along the optical axis such that adistance between the first lens group G1 and the second lens group G2, adistance between the second lens group G2 and the third lens group G3, adistance between the third lens group G3 and the fourth lens group G4, adistance between the fourth lens group G4 and the fifth lens group G5, adistance between the fifth lens group G5 and the sixth lens group G6 anda distance between the sixth lens group G6 and the seventh lens groupG7, are varied.

In the variable magnification optical system according to the presentExample, focusing from an infinite distance object to a close distanceobject is carried out by moving the fourth lens group G4, the fifth lensgroup G5 and the sixth lens group G6 independently from each other alongthe optical axis toward the object as respective focusing lens groups.

Table 8 below shows various values of the variable magnification opticalsystem relating to the present Example.

TABLE 8 Eighth Example [Surface Data] m r d nd νd OP ∞ 1 250.0000 2.9001.74389 49.53 *2 28.0269 12.424  3 154.1167 2.100 1.59349 67.00 432.5416 6.969 2.00069 25.46 5 61.8764 Variable 6 175.0869 5.997 1.8160046.59 7 −52.8034 1.500 1.85000 27.03 8 −204.9882 1.000 9 45.2860 1.5001.80518 25.45 10 26.6188 11.527  1.60300 65.44 11 −76.6492 Variable 12(S) ∞ 2.465 13 −64.5009 1.300 1.90265 35.72 14 −217.6883 0.200 15−214.1041 1.300 1.67270 32.18 16 26.6878 6.400 1.80809 22.74 17 502.6822Variable 18 65.6282 5.000 1.48749 70.32 19 −65.3105 Variable 20 −52.08511.300 1.84666 23.80 21 −201.9547 Variable 22 185.0000 5.300 1.5891361.15 *23 −50.5905 Variable *24 −27.3977 1.500 1.58913 61.15 25 −49.4756BF I ∞ [Aspherical Data] m: 2 κ = 0.0000 A4 = 3.95960E−06 A6 =3.76748E−09 A8 = −5.23494E−12  A10 = 1.04782E−14 A12 = −4.82160E−18  m:23 κ = 1.0000 A4 = 6.76320E−06 A6 = −8.33082E−09  A8 = 3.88079E−11 A10 =−7.09278E−14  m: 24 κ = 1.0000 A4 = 5.00393E−06 A6 = −8.92918E−09  A8 =2.86537E−11 A10 = −5.32582E−14  [Various Data] Variable magnificationratio 2.99 W M T f 22.7 50.0 67.9 FNO 3.03 3.00 3.03 2ω 91.04 45.9633.62 Ymax 19.30 21.60 21.60 TL 188.49 155.49 167.35 BF 16.20 23.3732.67 W M T W M T INF INF INF CLO CLO CLO d5 64.883 10.266 5.946 64.88310.266 5.946 d11 2.200 12.775 27.038 2.200 12.775 27.038 d17 20.0358.462 6.571 19.026 7.439 4.593 d19 2.030 3.706 4.816 1.360 3.164 4.349d21 4.601 9.046 14.467 4.908 8.936 15.092 d23 7.862 17.178 5.159 9.23418.853 6.979 [Lens Group Data] Group ST f 1 1 −42.744 2 6 40.599 3 12−105.371 4 18 68.000 5 20 −83.229 6 22 68.000 7 24 −106.909 [Values forConditional Expressions] (1) (−f1)/f1Rw = 0.885 (2) BFw/fw = 0.713 (3)|fF|/ft = 1.001 (4) f1N/f1 = 0.998 (5) D1Mw/fw = 2.858 (6) νM1P/νM1N =2.421 (7) fM1P/fM1N = 0.456 (8) ωw = 45.52°

FIG. 23A, FIG. 23B and FIG. 23C are graphs showing various aberrationsupon focusing on an infinite distance object, respectively, in the wideangle end state, in the intermediate focal length state and in thetelephoto end state, of the variable magnification optical systemaccording to the Eighth Example.

FIG. 24A, FIG. 24B and FIG. 24C are graphs showing various aberrationsupon focusing on a close distance object, respectively, in the wideangle end state, in the intermediate focal length state and in thetelephoto end state, of the variable magnification optical systemaccording to the Eighth Example.

As is apparent from the above-mentioned graphs showing variousaberrations, the variable magnification optical system relating to thepresent Example can correct superbly various aberrations over the wideangle end state to the telephoto end state and has excellent imagingperformance, and further has excellent imaging performance even uponfocusing on a close distance object.

According to each of the above described Examples, it is possible torealize a variable magnification optical system that has focusing lensgroup (s) which is (are) light in weight and downsized and which cansuppress superbly variations in aberrations upon varying magnificationfrom a wide angle end state to a telephoto end state and variations inaberrations upon carrying out focusing from an infinite distance objectto a close distance object. In this variable magnification opticalsystem, since the focusing lens group(s) is(are) made small in size andlight in weight, driving mechanism for the focusing lens group(s)is(are) also downsized, so it is possible to realize high speed as wellas noiseless focusing operation without making lens barrel large.

Meanwhile, it is noted that each of the above described Examples is aconcrete example of the invention of the present application, and theinvention of the present application is not limited to them. Thecontents described below can be adopted appropriately withoutdeteriorating optical performance of the variable magnification opticalsystems according to the present embodiment.

Although variable magnification optical systems having a five groupconfiguration, a six group configuration, and a seven groupconfiguration, were illustrated above as numerical examples of thevariable magnification optical systems according to the presentapplication, the invention of the present application is not limited tothem and variable magnification optical systems having otherconfigurations, such as eight group configuration or the like, can beconfigured. Concretely, a lens configuration that a lens or a lens groupis added to the most object side or the most image side of the variablemagnification optical system according to each of the above describedExamples is possible. Alternatively, a lens or a lens group may be addedbetween the first lens group Gland the first intermediate lens groupGM1. Alternatively, a lens or a lens group may be added between thefirst intermediate lens group GM1 and the second intermediate lens groupGM2. Alternatively, a lens or a lens group may be added between thesecond intermediate lens group GM2 and the rear lens group GR.

Further, in each of the above described Examples, configurations thatthe first intermediate lens group GM1 is composed of the second lensgroup G2 or of the second lens group G2 and the third lens groups G3,were illustrated, but configurations are not limited to them. Further,in each of the above described Examples, configurations that the secondintermediate lens group GM2 is composed of the third lens group G3, orof the fourth lens group G4, or of the third lens groups G3 and thefourth lens group G4, were illustrated, but configurations are notlimited to them.

Further, in each of the above described Examples, one, two or three lensgroups, are adopted as focusing lens groups, but a part in lens group,or four or more lens groups may be adopted for focusing lens group(s).Each of the focusing lens groups may be composed of one or two lenscomponents, and a configuration composed of one lens component is morepreferable. Auto focusing can be applied for such focusing group(s), anddrive by motor for auto focusing, such as, ultrasonic motor, steppingmotor, and VCM motor may be suitably adopted.

Further, in the variable magnification optical systems according to eachof the above described Examples, any lens group in the entirety thereofor a portion thereof can be moved in a direction including a componentperpendicular to the optical axis as a vibration reduction lens group,or rotationally moved (swayed) in an in-plane direction including theoptical axis, whereby a configuration of a vibration reduction can betaken.

Further, in the variable magnification optical systems according to eachof the above described Examples, a lens surface of a lens may be aspherical surface, a plane surface, or an aspherical surface. When alens surface is a spherical surface or a plane surface, lens processing,assembling and adjustment become easy, and it is possible to preventdeterioration in optical performance caused by lens processing,assembling and adjustment errors, so that it is preferable. Moreover,even if an image plane is shifted, deterioration in depictionperformance is little, so that it is preferable. When a lens surface isan aspherical surface, the aspherical surface may be fabricated by agrinding process, a glass molding process that a glass material isformed into an aspherical shape by a mold, or a compound type processthat a resin material is formed into an aspherical shape on a glass lenssurface. A lens surface may be a diffractive optical surface, and a lensmay be a graded-index type lens (GRIN lens) or a plastic lens.

Further, in the variable magnification optical systems according to eachof the above described Examples, it is preferable that the aperture stopS is disposed between the second lens group G2 and the third lens groupG3, or between the third lens group G3 and the fourth lens group G4.But, the function may be substituted by a lens frame without disposing amember as an aperture stop.

Moreover, the lens surface(s) of the lenses configuring the variablemagnification optical system according to each of the above describedExamples, may be coated with anti-reflection coating(s) having a hightransmittance in a wide wavelength region. With this contrivance, it isfeasible to reduce a flare as well as ghost and attain excellent opticalperformance with high contrast.

Next, a camera equipped with the variable magnification optical systemaccording to the present embodiment, will be explained with referring toFIG. 25. FIG. 25 is a view showing a configuration of the cameraequipped with the variable magnification optical system according to thepresent embodiment. The camera 1, as shown in FIG. 25, is a so-calledmirror-less camera of a lens interchangeable type equipped with thevariable magnification optical system according to the first Example asan imaging lens 2.

In the present camera 1, a light emitted from an unillustrated object(an object to be photo-taken) is converged by the imaging lens 2,through a unillustrated OLPF (Optical low pass filter), and forms animage of the object on an imaging plane of an imaging portion 3. Thelight from the object is photo-electrically converted through aphoto-electric conversion element provided on the imaging portion 3 toforma picture image of the object. This picture image is displayed on anEVF (electric view finder) 4 provided on the camera 1. Accordingly, aphotographer can observe the object to be photo-taken through the EVF.

Further, upon unillustrated release button being depressed by thephotographer, the picture image of the object formed by the imagingportion 3 is stored in an unillustrated memory. Thus, the photographercan take a photo of the object by the camera 1.

It is noted here that the variable magnification optical system relatingto the First Example mounted on the camera 1 as the imaging lens 2, hassuperb optical performance as described above and the focusing lensgroup(s) is (are) made light in weight and small in size. In otherwords, by making the focusing lens group (s) small in size and light inweight, high speed focusing can be realized, and it is possible toattain superb optical performances that variations in aberrations uponvarying magnification from the wide angle end state to the telephoto endstate as well as variations in aberrations upon carrying out focusingfrom an infinite distance object to a close distance object, can besuppressed.

Incidentally, even in a case where a camera in which the variablemagnification optical system according to any of the before-mentionedSecond to Eighth Examples is installed as the imaging lens 2, isconfigured, the camera also can the same effects as those of theabove-mentioned camera 1. Further, even when the variable magnificationoptical system according to any of the Examples is installed in a cameraof a single lens reflex type equipped with a quick return mirror inwhich the object image is observed through a finder optical system, thecamera also can have the same effects as those of the above-mentionedcamera 1.

Next, an outline of a method for manufacturing the variablemagnification optical system according to the present embodiment, isdescribed with referring to FIG. 26. FIG. 26 is a flowchartschematically showing a method for manufacturing the variablemagnification optical system.

The method for manufacturing the variable magnification optical systemaccording to the present embodiment shown in FIG. 26, is a method formanufacturing a variable magnification optical system which comprises,in order from an object side, a first lens group having negativerefractive power, a first intermediate lens group having positiverefractive power, a second intermediate lens group having negativerefractive power and a rear lens group; the method comprising thefollowing steps S1 to S3.

Step S1: constructing such that, upon varying magnification from a wideangle end state to a telephoto end state, a distance between said firstlens group and said first intermediate lens group is varied, a distancebetween said first intermediate lens group and said second intermediatelens group is varied, and a distance between said second intermediatelens group and said rear lens group is varied.

Step S2: constructing such that said rear lens group comprises at leastone focusing lens group which is moved upon carrying out focusing froman infinite distance object to a close distance object.

Step S3: constructing such that said variable magnification opticalsystem satisfies the following conditional expressions (1) and (2):

0.40<(−f1)/f1Rw<2.00  (1)

0.10<BFw/fw<1.00  (2)

where f1 denotes a focal length of said first lens group, f1Rw denotes acomposite focal length of all lens groups behind said first lens groupin the wide angle end state, BFw denotes a back focus of said variablemagnification optical system in the wide angle end state, and fw denotesa focal length of said variable magnification optical system in the wideangle end state.

According to the above-stated method for manufacturing the variablemagnification optical system according to the present embodiment, it ispossible to realize a variable magnification optical system in whichfocusing lens group(s) is(are) downsized and reduced in weight and whichcan superbly suppress variations in aberrations upon varyingmagnification from the wide angle end state to the telephoto end stateas well as variations in aberrations upon carrying out focusing from aninfinite distance object to a close distance object.

EXPLANATION OF REFERENCE SYMBOLS

-   -   G1 first lens group    -   G2 second lens group    -   G3 third lens group    -   G4 fourth lens group    -   G5 fifth lens group    -   G6 sixth lens group    -   G7 seventh lens group    -   GM1 first intermediate lens group    -   GM2 second intermediate lens group    -   GR rear lens group    -   S aperture stop    -   I image plane

1. A variable magnification optical system comprising, in order from anobject side, a first lens group having negative refractive power, afirst intermediate lens group having positive refractive power, a secondintermediate lens group having negative refractive power and a rear lensgroup; upon varying a magnification from a wide angle end state to atelephoto end state, a distance between said first lens group and saidfirst intermediate lens group being varied, a distance between saidfirst intermediate lens group and said second intermediate lens groupbeing varied, and a distance between said second intermediate lens groupand said rear lens group being varied; said rear lens group comprisingat least one focusing lens group which is moved upon carrying outfocusing from an infinite distance object to a close distance object;and the following conditional expression being satisfied:0.40<(−f1)/f1Rw<2.00 where f1 denotes a focal length of said first lensgroup, and f1Rw denotes a composite focal length of all lens groupsbehind said first lens group in the wide angle end state.
 2. A variablemagnification optical system according to claim 1, wherein the followingconditional expression is satisfied:0.70<|fF|/ft<3.30 where fF denotes a focal length of a focusing lensgroup having a strongest refractive power in the focusing lens groups,and ft denotes a focal length of the variable magnification opticalsystem in the telephoto end state.
 3. A variable magnification opticalsystem according to claim 1, wherein the following conditionalexpression is satisfied:0.60<f1N/f1<2.00 where f1N denotes a focal length of a lens having astrongest negative refractive power in the first lens group, and f1denotes a focal length of the first lens group.
 4. A variablemagnification optical system according to claim 1, wherein the followingconditional expression is satisfied:2.00<D1Mw/fw<4.00 where D1Mw denotes a distance along the optical axisbetween the first lens group and the first intermediate lens group inthe wide angle end state, and fw denotes a focal length of the variablemagnification optical system in the wide angle end state.
 5. A variablemagnification optical system according to claim 1, wherein the followingconditional expression is satisfied:2.00<νM1P/νM1N<3.00 where νM1P denotes an Abbe's number of a lens havinga strongest positive refractive power in the first intermediate lensgroup, and νM1N denotes an Abbe's number of a lens having a strongestnegative refractive power in the first intermediate lens group.
 6. Avariable magnification optical system according to claim 1, wherein thefollowing conditional expression is satisfied:0.20<fM1P/fM1N<0.80 where fM1P denotes a focal length of a lens having astrongest positive refractive power in the first intermediate lensgroup, and fM1N denotes a focal length of a lens having a strongestnegative refractive power in the first intermediate lens group.
 7. Avariable magnification optical system according to claim 1, wherein38.00°<ωw<85.00° where ωw denotes a half angle of view of the variablemagnification optical system in the wide angle end state.
 8. A variablemagnification optical system according to claim 1, wherein said focusinglens group is composed of one or two lenses.
 9. A variable magnificationoptical system according to claim 1, wherein said first intermediatelens group comprises at least two lenses having negative refractivepower.
 10. A variable magnification optical system according to claim 1,wherein said first lens group is composed of two lens components.
 11. Avariable magnification optical system according to claim 1, wherein saidrear lens group comprises at least one lens component at an image sideof the most image side focusing lens group in said focusing lens groups.12. A variable magnification optical system according to claim 1,wherein at least one of the focusing lens groups has positive refractivepower.
 13. A variable magnification optical system according to claim 1,wherein said first intermediate lens group comprises, in order from theobject side, a second lens group having positive refractive power and athird lens group having positive refractive power.
 14. A variablemagnification optical system according to claim 1, wherein said rearlens group comprises at least two focusing lens groups.
 15. An opticalapparatus comprising a variable magnification optical system accordingto claim
 1. 16. A method for manufacturing a variable magnificationoptical system which comprises, in order from an object side, a firstlens group having negative refractive power, a first intermediate lensgroup having positive refractive power, a second intermediate lens grouphaving negative refractive power and a rear lens group, comprising thesteps of: constructing such that, upon varying a magnification from awide angle end state to a telephoto end state, a distance between saidfirst lens group and said first intermediate lens group is varied, adistance between said first intermediate lens group and said secondintermediate lens group is varied, and a distance between said secondintermediate lens group and said rear lens group is varied; constructingsuch that said rear lens group comprises at least one focusing lensgroup which is moved upon carrying out focusing from an infinitedistance object to a close distance object; and constructing such thatthe following conditional expression is satisfied:0.40<(−f1)/f1Rw<2.00 where f1 denotes a focal length of said first lensgroup, and f1Rw denotes a composite focal length of all lens groupsbehind said first lens group in the wide angle end state.
 17. A variablemagnification optical system according to claim 1, wherein the followingconditional expression is satisfied:0.10<BFw/fw<1.00 where BFw denotes a back focus of said variablemagnification optical system in the wide angle end state, and fw denotesa focal length of said variable magnification optical system in the wideangle end state.